errors with structure save and load function - c

Question

#include <stdio.h>
#include <stdlib.h>
struct birdhome{
int area;
int heightcm;
int feederquantity;
char hasNest[6];
};
struct bird{
char isRinged[6];
char nameSpecies[50];
int birdAgeMonths;
struct BirdHome *hom;
char gender[7];
};
int save(char * filename, struct bird *st, int n);
int load(char * filename);
int main(void)
{
char * filename = "birds.dat";
struct bird birds[] = { "True","sparrow",3,10,20,2,"False","Male","False","crane",24,50,100,6,"True","Female","False","False","griffin",10,100,80,1,"False","Male" };
int n = sizeof(struct bird) / sizeof(birds[0]);
save(filename, birds, n);
load(filename);
return 0;
}
int save(char * filename, struct bird * st, int n)
{
FILE * fp;
char *c;
int size = n * sizeof(struct bird);
if ((fp = fopen(filename, "wb")) == NULL)
{
perror("Error occured while opening file");
return 1;
}
c = (char *)&n;
for (int i = 0; i<sizeof(int); i++)
{
putc(*c++, fp);
}
c = (char *)st;
for (int i = 0; i < size; i++)
{
putc(*c, fp);
c++;
}
fclose(fp);
return 0;
}
int load(char * filename){
FILE * fp;
char *c;
int m = sizeof(int);
int n, i;
int *pti = (int *)malloc(m);
if ((fp = fopen(filename, "r")) == NULL)
{
perror("Error occured while opening file");
return 1;
}
c = (char *)pti;
while (m>0)
{
i = getc(fp);
if (i == EOF) break;
*c = i;
c++;
m--;
}
n = *pti;
struct bird * ptr = (struct bird *) malloc(n * sizeof(struct bird));
c = (char *)ptr;
while ((i= getc(fp))!=EOF)
{
*c = i;
c++;
}
printf("\n%d birds in the file stored\n\n", n);
for (int k = 0; k<n; k++)
{
printf("%-10d %-6s %-50s %-24d %-100d %-100d %-10d %-10s %-10s \n", k + 1, (ptr + k)->isRinged, (ptr + k)->nameSpecies,(ptr + k)->birdAgeMonths,(ptr + k)->hom.area,(ptr + k)->hom.heightcm,(ptr + k)->hom.feederquantity,(ptr + k)->hom.hasNest,(ptr + k)->gender);
}
Well, the program is theoretically running. The problem is with the printf inside the load function.
The error says that all the structure types that come in struct Birdhome is a
pointer and that I should use -> instead of . in it.
But when I do this it says that I should change the . to ->.

Answer 1

The problem is that bird.hom is a pointer. Saving a pointer to a file is not a useful thing to do, because memory addresses change from one process to another. It's also not saving the contents of the BirdHome structure. And your initialization of birds doesn't work, because you can't initialize members of an indirect structure as part of the main structure.
You should declare it as an embedded structure rather than a pointer.
struct bird{
char isRinged[6];
char nameSpecies[50];
int birdAgeMonths;
struct BirdHome hom;
char gender[7];
};
Declaring it as a pointer would be useful if you wanted a dynamically-sized array of homes, or you wanted to allow multiple birds to reference the same BirdHome structure. If that's what you really need, you'll need to redesign your save and load functions so they dereference the pointer and save what it points to. And if you have a dynamically-sized array of BirdHome, you need to include the array size in bird.
Other errors in your code:
You have an extra "False" in the initialization list of birds. It should be:
struct bird birds[] = { "True","sparrow",3,10,20,2,"False","Male","False","crane",24,50,100,6,"True","Female","False","griffin",10,100,80,1,"False","Male" };
Your calculation of n is incorrect. It should be:
int n = sizeof(birds) / sizeof(birds[0]);